The present invention relates generally to liquid level measuring devices, and particularly those of the bubble tube type.
The present invention resides in the provision of a unique bubble tube type measuring device which overcomes the well-known disadvantages of float type measuring devices (i.e., expense, reliability, accuracy, etc.), which is extremely reliable and accurate in operation and yet is very easy to use, and which is capable of selectively monitoring almost any number of liquid-containing tanks, regardless of the viscosity of the liquid therein.
The apparatus functions by supplying an accurately measured quantity of purge gas at an accurately controlled predetermined pressure and flow rate through a selector valve to a tube extending to the bottom of any one of a number of liquid-containing tanks to be monitored. The purging is done in two stages to increase the speed of operation. When the device is actuated, the first stage of purge gas is at a relatively high pressure and flow rate for intially clearing the tube of substantially all liquid originally disposed therein, and the second stage of purge gas is a fixed volume is at a lower pressure and flow rate (which is constant) for stabilizing the system at a pressure which accurately reflects the liquid depth in the tank. The device utilizes a source of purge gas which is readily available in replaceable/disposable containers. it is completely safe to use even with highly inflammable liquids (e.g. gasoline fuel, etc.), and when used to measure oil in an engine sump, may be operated even when the engine is running. The device is also accurate at any altitude, and has a "check" mode for diagnostic purposes.
Other objects and advantages of the present invention will become apparent upon a reading of the detailed description of the preferred embodiment taken in conjunction with the accompanying drawings and the appended claims.